Control system and apparatus



H. A. LEWIS. CONTROL SYSTEM AND APPARATUS.

APPLICATION FILED MAY 23, 1.919.

Patented Aug. 16, 1921.

INVENTOR f/arry/iLew/s BY wnuzssss: a.

ATTORNEY 1,387,498. I v 7 Original application filed May 22, 1911,

VUNITED, STA

Tss PATENT OFFICE. i

' HARRY A. LEWIS, ornonars'rown, PENNSYLVANIA,-IASSIGNORTO WESTINGHOUSE ELECTRIC ANnMan'UrAcTUnIN coMP NY ,'AcoRPoR-A1ioN or PENNSYL CONTROL SYSTEM AND APPARATUS.

To all whomz'tmag concern:1 I

I is a specification, thisapplication being a filed hiay 22, 191 1.

division of application SerialNo. 628,733,

My invention relates generally to electromagnets and electromagnetic switches for the control oi electric circuits, and more particularly to switches for controlling electric motors and to the motor circuits controlled thereby. I I

An object 01 my invention is toprovide an electromagnet comprising a pair or? connected cooperating COIlS and a movable arniature orcore member that shall be actuated by the eneiigization of said coils within predetermined limits only. 3

A second object otmyim'ention is to provide an electromagnetic, switch operable by an electromagnet having the characteristics above referred to.

A third object of my invention is to pro- 7 vide a motor-control system employing an electromagnetic switchv the above-designatedcharacter. a v i I Other objects of-myinvention Willi-appear hereinafter. I In my co-pendingapplication Serial No. 628,733, filed' May 22,1911, resultingin Patent No. 1,339,900, May 11, 1920, I have disclosed various types of electromagnets and electromagnetic switches that are adapted for use in unit switchcontrol systems. One

such switch is there shownas controlledby a series and a shunt coil and a second by a single series coil. A thirdswitch is there described as controlled by a'plur'ality of series coils. y p y f The present application, whichis a division of my above-mentioned application, relates more partieularlyto electromagnets and electromagnetic switches having a plurality of series coils and to motor-controlsystemsembodying such devices. The use of the customary shunt coils'and the compli cated control mechanisms attendant thereupon are thus avoided, j

Figure lot the accompanying drawings p is a partly sectional elevation of an electro- 1 Specification of Letters Patent.

the inset portions 13 and 14- are, for con- Patented Aug. 16, 1921.

Serial No. 628,733. Divided and this application filed May 23, 1919. Serial No. 298,251.

magnetic switch embodying my invention, and Flg. 2 is a diagrammatic View of a control system employing my electromagnetic switch and arranged according to my invention. 7

Referring to Fig. 1 of the drawings, the switch here shown comprises a stationary magnetizable member 1, movable magnetizable members 2 and 3, stationary switch contact members i and 5, movable switch contact members 6 and 7 and actuating coils 8 and "9 connected in -series. The number of turns of thecoil 8 is preferably greater than that of the coil 9, so that, as the current traversing said coils decreases in value, the strength of the magnetic field of the coil 9 decirgases more rapidly than that /of the cor The stationary member 1 is rectangular in form and comprises a central branch 10 of relatively large cross-section, on which the colls 8 and 9 are both mounted, and side branches 11 and 12, which are connected, through the branches 28 and 29", to the ends of the branch 10 outside of the coils 8 and9, and are inset atl3 and 14 between the coils so that they come into contact, or

branch 10 at these points.

The portions of the side branches 11 and 12 which extend to venience, labeled 29 and 28 The branches I Q-SHnay be provided with air aps.

The movable members 2 an 3 are alike and comprise arms 15 and 16 that are'pivotally secured to the stationary member 1 atv 17 and 18 and are disposed substantially parallel to the side branches 11 and 12. The said arms are severally provided with lateral! projections 19 and 20 that extend into recesses 21 and 22'fo'rmed by the inset portions 13 and 14 of the side branches l1 and 12 of the stationary member 1, inwardly proj ecting arms 23 and 24: and contact-bearing arms 25* and 26 to which the members 6 and 7 are attached. The widths of theair ga s between the ends'of the projections 19 and 20 and the inset portions 13 and 14 are determined by adjusting screws 27 and 27* with which the lower ends of the arms 15 and 16 are provided. 7

As stated in my above-mentioned application, the coils Sand 9 may be connected to 'crosssectional area), it will 'fiux ot the coil 9 cally as a single coil or they may have dif- :terent structural and functional characteristics. According to my present invention, however, the two coils are electrically connected in series and are wound in the same direction.

The magnetic flux established by the coil 8 traverses the circuits comprising the central branch 10. tl e side branches 11 and 12 and the branches 52S and the portions 29. That portion of the stationary magnetizable member 1 which is included in the circuits becomes energized to attract the armatures J3 and. and being of magnetizable material, it will ten-c to maintain the flux within its own confines. It the flux, however, is above a predetermined value, sufliciently large to saturate the alj o ve-traced circuits (For the branches 11 and. 12 are of limited traverse additional circuits comprising the central branch the inset portions 13 and 11, the recesses 91 and 22. the side branches 11 and 12 and tne branches 28. The flux will leak beyond the confines of the circuits just t-aced to enter the projections 19 and 20, the arms and 16 and the arnnitures 23 and 21. This leakage flux will aid the magnetism of the saturated circuits to close the switch members. The llllX will even traverse the full length of the central branch 1.0, continuing by way or the banches 29" and the lower portions oi the branches 11 and 12. across the recesses 21 and 29. This path is rendered particularly easy of travel because of the is in the same direction as that of the coil 8. The excess or leakage flux traversing the recesses 21 and will, of course, act upon the projections 19 and with forces opposing the forces acting upon the armatures and 2%. The coil 9, fun thermore, exerts a greater torce upon the branches 15 and 16 than the coil 8 because of its greater distance from the pivotal points 17 and 18. On the other hand, the coil 9 exerts no force at all upon the armatures 23 and 2 1.

The operation of the electromagnet and ot the switch contact members actuated by it is as "follows: if the coil 8 were alone energized. the arms 23 and 2% would be attracted to the adjacentend oi" the branch 10 (the influence of the coil 8 over the arms and Elbeing' greater than that over the branches 11 and 12) and the switch contact members 0 "l 7 would bemoved into engagement w tie stationary contact member If, however, the coil 9 is also s and 5. energized a leakage magnetic flux will, as above described, traverse the air gaps provided by the screws Qitand 27 and either the arms and 16 and the central brancn 10 or portions of the arms 15 and 16 and the projections 19 and QOthat will be of suf icient strength to overbalance the pull upon the arms 23 and 24 and prevent the closing of the switch contact terminals until the current in the coils S and 9 falls below a predetermined value and the leakage flux value, in consequence, becomes considerably decreased. lVhen the said current reaches such predetermined value, the coil 8 will overpower the coil 9 and one of the movable members 2 and 3 will be actuated by the magnetic pull exerted upon the arms 23 and Let, and the corresponding switch will be closed.

It is evident that, it only a single pair oi: switch contacts is desired, only one 01 the movable members 2 and 3 is necessary. Theoretically, both of the movable members can be made to act at the same time by adjusting the air gaps with sutlicient care, but, practically, it is impossible to maintain such action under ordinary operating conditions and, consequently, I prefer to use a single movable member for one set of switch con tacts and, if two or more members are employed, to so adjust the air gaps that they will act successively to close two independent switches instead of acting together.

The operation or the switch shown in Fig. 1 will be considered more in detail in connection with the diagram of Fig. 2 in which energy is supplied to the motor #11 from any suitable source of electricity through line conductors i5 and 46, the direction of motor rotation being controlled by a reversing switch 90 and the acceleration of the motor being controlled by resister sections 51, 52, and 54 and magnet switches 91 and 92. which severally correspond to the switch of Fig. l.

1- ssuming that master switch 57 is moved to position a, energy is supplied from the line conductor 15, through the master switch conductor 93, coil 94 of the reversing switch 90. conductor 95, switch 57 and conductor 96 to opposite line conductor -16. lVhen coil 94: is energized, reversing switch arms 97 and 98 are moved in opposite directions away from each other. and the motor circuit is completed from conductor -15 through conductor 99, field-magnet winding 75, conductor 100, switch contact member 97, conductor 101, motor armature 67, conductor 102, switch contact member 98. conduct-or 103. series coils 72, 80, 79 and '73, resister sections 51 to 54:, inclusive, and conductor 106 to the other line conductor 46. Since the current traverses the coils 72, 80. 79 and 73, the magnet switches 91 and 92- will be quite strongly energized when the reversing switch is first closed and the motor circuit is first established, then, as the motor speed increases, the motor current will be materially reduced until the armature 107 of the switch 92 is actuated and the switch 108 is closed in accordance with the principles of operation outlined in' connection with the description of the device shown in Fig. 1.

As soon as switch 108 is closed, resistor section 54; is shunted by a circuit which extends from switch 108 through conductor 112, resistor section 54:, conductor 113 and armature member 107 to switch 108. The resulting increase in the motor current serves to still further delay the action of the armature 109 of the switch 92 and the armatures 110 and 111 of magnet switch 91, which will operate successively in'the order named to short-circuit the resistance sections 53, 52'and 51. The circuits for shunting the resistor sections 53, 52 and 51' are similar to that traced in connection with resistor section 54 and are apparent from an inspection oi? the drawing. The armatures are made to operate in the proper succession by adjusting the air gaps, as explained in connection with the magnet illustrated in Fig.

1. This result may also be obtained by providing the coils of the switches with different numbers of turns.

I claim as my invention: 1. An electromagnet comprising a stationary magnetizable member, a movable actuating said element and a magnet the leakage flux of which is adapted to prevent the actuation of said element.

3. The combination with a movable me1nber, of a plurality of series coils for creating a magnetic field for controlling said member and means controlled by the leakage flux of said field for preventing the actuation of said member.

et. The combination with a movable member, oi means comprising two series coils for creating aplurality of magnetic fields for controlling said member and means controlled by the leakage flux of said fields for preventing the actuation of said memher.

5. A magnet comprising two series coils and a magnetizable member having two positions, the leakage flux due to one of said coils tending to'maintain said member in one of said positions and the flux due to the other coil serving to maintain said member in said other position.

6. An electromagnetic switch having two series coils, means whereby the leakage flux due to one of said series coils tends to maintain said switch open and means whereby the flux due to the other series coil serves to maintain said switch closed.

:7. A controlling device for electric circuits comprising a switch member normally biased to open position, aplurality of means comprising two series coils for creating a magnetic field, and means whereby the leakage flux of said field holds the switch memher in open position.

8. An electromagnetic switch having two series coils for creating two supplementing magnetic fields, one of said fields opposing the closing of said switch and the other of said fields serving to hold said switch in closed position.

9. The combination with a movable member, of two series coils for creating two supplementing magnetic circuits for controlling said member, the leakage fiux of one of said circuits preventing the actuation of said member and said other circuit serving to hold said member in actuated position.

10. An electric switch having two series coils, means whereby the leakage flux produced by one of said coils tends to maintain said switch open and means whereby the leakage flux produced by the other of said other coils tends to close said switch.

11. The combination with a movable element, of a magnet having a series coil for exerting opposing forces upon said element and a magnet, the leakage flux of which is adapted to additionally act upon said element, in the direction of one of said forces.

12. The combination with an electric motor having an armature, and a source of current for said motor, of a switch for controlling said motor, a magnetizable member for controlling said switch, a coil connected in series with said armature for controlling both ends of said member, and a coil in series with said armature for controlling one end only of said member.

13. The combination with a movable member having two magnetizable portions,

of a series coil for both of said portions and a series coil for one only of said portions.

14. An electromagnetic switch provided with two coils having series characteristics for creating two magnetic fields adapted to act cumulatively to maintain said switch open in opposition to the force of the field of one of said coils.

15. An electromagnet switch comprising an armature, a series lockout coil acting upon said armature to maintain said switch open and a series closing coil acting oppositely upon said armature with forces adapted, respectively, to aid said lockout coil to maintain said switch open and to close said switch.

16. The combination with a magnetizable frame having a recess, of an armature having a projection adapted to extend into said I recess and means comprising two series coils for energizing said frame to act oppositely upon said armature and said pro ect1on.

17. The combination with a pair of relatively movable magnetizable members, of two series coils 'for energizing said magnetizablc members with magnetism of one polarit f, said magnetism having a normal liur; path that tends to produce relative movement between id members and a leakage flux path that tends to prevent relative movement between said members.

18. The combination with a pair of coaxial separately mounted series coils, t an armature of U-shape, one of the legs of which extends between said coils and the other leg of which is adapted to be attracted one of said coils.

19. in a system of motor control. the combination with a motor and an accelerating resistance, of a magnet en :h for gover .ing the i1 ance having a s tionar magnetizable member. taiiiona itch contact members, movable magnet 2a b rs contact men it s secured thereto and a current coil tending to actuate the movable members and close the switches, am; a current coil operating in the same cirec ion electrically but opposing the action or ible members when the motor current exceeds a predetermined amount.

20. In a stem of motor control, the con bination w h a motor a ving an armature and an accelerating resistor in circuit therewith. and a source of currei t for said motor, of a magnet switch for governing said resistor having a coil in series with said a; true, means wherebv the leakage flux of s series coil maintains said switch open when the current traversing said motor exceeds a predetermined value, and a second series coil for maintaining said switch closed.

21. The combination with a movable element, of means comprising a series coil tending to maintain said element in a predeten mined position and a magnet comprislng a series coil the leakage flux of which is adapted to prevent the actuation of said element to said predetermined position.

22. The combination with a movable element, of an electromagnet comprising a series energizing coil for exerting opposing forces upon said element and an electromagnet for additionally acting upon said element in the direction of one of said forces.

23. An electromagnetic switch having a movable switch member, electromagnetic means comprising a series coil for closing said member and for compensating for variations in the degree of energization of said electromagnetic means, and electromagnetic means for opposing the movement of said member.

24. An electromagnetic switch having a movable member, electromagnetic means comprising a series coil for actuating the same and for compensating for variations in the actuating force because of variations in the value of the current traversing said coil, and a series lockout electromagnet :t'or opposing the movement of said member.

In testimony whereof I have hereunto subscribed my name this 16th day of May, 1919.

HARRY A. LEWIS. 

